currently, polystyrene board (eps), extruded board (xps), polyurethane rigid foam (pu) three organic materials. among them, pu is currently recognized as the best thermal insulation material in the world. its thermal conductivity is the lowest among all thermal insulation materials and it has the most superior thermal performance. when the density of rigid polyurethane is 35~40 kg /m3, its thermal conductivity is only 0.018~0.023 w/(m.k), and the thermal insulation effect of 25 mm thick polyurethane rigid foam is equivalent to 40 mm thick eps, 45 mm mineral wool, 380 mm thick concrete or 860 mm ordinary brick. under the same insulation effect, the insulation thickness is about half that of eps.
the report points out that one of the reasons for the rapid spread of the fire is that the polyurethane insulation materials and simulated green plants used in hangzhou ice and snow world are not non-combustible , flame retardant requirements, the smoke spreads quickly after a fire. the second is that the fire separation measures and smoke prevention measures between hangzhou ice and snow world and other areas in the building are not in place. the inner wall is made of polyurethane sandwich color steel plate, and the exit door of the place is replaced by a fireproof door, which leads to a fire. it quickly spread to the entire second floor.
one of the causes of casualties is that after the fire broke out, materials such as polyurethane and simulated green plants burned in a large area, resulting in a large amount of high-temperature and toxic smoke, the combustible smoke released continues to accumulate, deflagration occurs, resulting in casualties.
for a while, polyurethane insulation materials once again became the target of public criticism and fell into a storm of public opinion!
thinking about this passage carefully, the words are a bit biased, and there are two inappropriate points.
one: polyurethane insulation materials and simulated green plants are not non-combustible and non-combustible fuel requirements.
according to the "classification method for the combustion behavior of building materials" (gb8624-1997), polyurethane meets the requirements of b2 level, and can be used after adding special flame retardants reach b1 grade polyurethane insulation board. although polyurethane insulation boards have the characteristics of organic materials, under the current technical conditions, the highest can only reach the judgment of flame retardant grade b1. moreover, there are technical bottlenecks and difficulties in the research and development and manufacture of b1 grade polyurethane insulation boards. the polyurethane insulation boards produced by most small and medium-sized enterprises can only reach b2 grade or even b3 grade. however, there are still several large domestic production companies that can still do it. polyurethane insulation board is made by combining polyether and polymeric mdi (polyphenyl polymethylene polyisocyanate) for foaming reaction. it is determined that the flame retardancy level is b1 through the gb8624-2012 standard inspection. insulation materials. it is mainly used in the fields of building enclosure energy saving and large-scale cold storage and cold chain insulation. at the same time, it can also be used for fire prevention and heat insulation in industrial plants, ships, vehicles, military water conservancy construction and other fields.
second: after a fire, the smoke spreads quickly and the polyurethane insulation material is poisonous.
the toxicity of polyurethane used to be a controversial issue, especially�it is when accidents such as polyurethane burning occur. the industry has a unified understanding that cured polyurethane is a non-toxic material, and some medical polyurethane materials have been used in human implants and medical device components. but uncured polyurethane has certain toxicity. rigid polyurethane foam is a thermosetting thermal insulation material. when it is burned in a fire, a carbonized layer is formed on its surface, and the carbonized layer can prevent the flame from spreading. eps and xps are thermoplastic materials that will melt and drip when exposed to fire, and these drips can also burn.
fire is not caused by insulation materials only, but the building should be considered as a system, how is the fire performance of the whole system, construction management and daily maintenance are very critical, and blindly emphasizing the fire rating of building materials itself is of little significance. ""actually, the material itself is fine, the key is to use it correctly and well. "as early as many years ago, li jianbo, deputy secretary-general of the china polyurethane industry association, emphasized similar problems many times in various industry forums and seminars, emphasizing the chaotic management of the construction site and the ineffective supervision of unqualified and non-compliant products on the wall. the main factor causing the fire is not to hit the board on the material as soon as there is a problem, so even now, the problem still exists, blindly letting the polyurethane insulation material take the blame, the editor thinks the conclusion is too biased.
